Non-aqueous electrolyte secondary battery having separator with multilayer structure

Abstract

A non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The separator has a multilayer structure in which a first filler layer containing phosphate particles, a porous resin substrate, and a second filler layer containing inorganic particles having higher heat resistance than the phosphate particles are stacked in this order from the negative electrode side. The first filler layer is disposed on the porous resin substrate in such a manner that the surface of the first filler layer faces the surface of the negative electrode. The phosphate particles have a BET specific surface area in the range of 5 m2/g or more and 100 m2/g or less.

The invention claimed is: 
     
       1. A non-aqueous electrolyte secondary battery comprising: a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode,
 wherein the separator has a multilayer structure including a porous resin substrate, a first filler layer containing phosphate particles, and a second filler layer containing inorganic particles having higher heat resistance than the phosphate particles, 
 the second filler layer is disposed on the porous resin substrate, 
 the first filler layer is disposed on the porous resin substrate or the second filler layer in such a manner that a surface of the first filler layer faces a surface of the negative electrode, and 
 the phosphate particles have a BET specific surface area in a range of 5 m 2 /g or more to 100 m 2 /g or less, 
 wherein a porosity of the porous resin substrate is in a range of 30% or more to 70% or less, 
 wherein the phosphate particles have an average particle size that is smaller than an average pore size of the porous resin substrate and that is in a range of from 0.05 μm to 1 μm, 
 wherein the first filler layer comprises a continuous layer configured to cover an entirety of a surface of the porous resin substrate or the second filler layer on which the first filler layer is disposed, 
 wherein the phosphate particles are configured to melt and flow into pores of the porous resin substrate and simultaneously to undergo polycondensation to form a coating film of a phosphate polycondensation product on the negative electrode in response to an exothermic reaction on a surface of the negative electrode, and 
 wherein a porosity of the first filler layer is 30% or more and 70% or less. 
 
     
     
       2. The non-aqueous electrolyte secondary battery according to  claim 1 , wherein the first filler layer, the porous resin substrate, and the second filler layer in the separator are stacked in this order from a negative electrode side. 
     
     
       3. The non-aqueous electrolyte secondary battery according to  claim 1 , wherein the first filler layer, the second filler layer, and the porous resin substrate in the separator are stacked in this order from a negative electrode side. 
     
     
       4. The non-aqueous electrolyte secondary battery according to  claim 1 , wherein the phosphate particles have a BET specific surface area in a range of 20 m 2 /g or more to 100 m 2 /g or less. 
     
     
       5. The non-aqueous electrolyte secondary battery according to  claim 1 , wherein the phosphate particles comprise at least one selected from dilithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium phosphate. 
     
     
       6. The non-aqueous electrolyte secondary battery according to  claim 3 , wherein the phosphate particles have an average particle size that is smaller than an average particle size of the inorganic particles and that is in a range of from 0.05 μm to 1 μm. 
     
     
       7. A non-aqueous electrolyte secondary battery comprising: a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode,
 wherein the separator has a multilayer structure including a porous resin substrate, a first filler layer containing phosphate particles, and a second filler layer containing inorganic particles having higher heat resistance than the phosphate particles, 
 the second filler layer is disposed on the porous resin substrate, 
 the first filler layer is disposed on the porous resin substrate or the second filler layer in such a manner that a surface of the first filler layer faces a surface of the negative electrode, 
 the phosphate particles have a BET specific surface area in a range of 5 m 2 /g or more to 100 m 2 /g or less, 
 wherein a porosity of the porous resin substrate is in a range of 30% or more to 70% or less, 
 wherein a thickness of the porous resin substrate is in a range of 3 μm or more to 20 μm or less, 
 wherein the first filler layer comprises a continuous layer configured to cover an entirety of a surface of the porous resin substrate or the second filler layer on which the first filler layer is disposed, 
 wherein the phosphate particles are configured to melt and flow into pores of the porous resin substrate and simultaneously to undergo polycondensation to form a coating film of a phosphate polycondensation product on the negative electrode in response to an exothermic reaction on a surface of the negative electrode, and 
 wherein a porosity of the first filler layer is 30% or more and 70% or less.